This invention relates to the disproportionation of olefin hydrocarbons. In another aspect this invention relates to the use of a rhenium oxide catalyst.
Disproportionation is used herein to denote the conversions of olefin hydrocarbons which can be visualized as comprising the reaction between two first pairs of carbon atoms, the two carbon atoms of each first pair being connected by an olefinic double bond, to form two new pairs from the carbon atoms of said first pairs, the two carbon atoms of each said new pairs being connected by an olefinic double bond. Typical disproportionation reactions include:
(1) The disproportionation of an acyclic mono- or polyene having at least three carbon atoms into other acyclic mono- or polyenes of both higher and lower number of carbon atoms; for example, the disproportionation of propylene yields ethylene and butenes; the disproportionation of 1,5-hexadiene yields ethylene and 1,5,9-decatriene;
(2) The conversion of an acyclic mono- or polyene having three or more carbon atoms and a different acyclic mono- or polyene having three or more carbon atoms to produce different acyclic olefins; for example, the conversion of propylene and isobutylene yields ethylene and isopentene;
(3) The conversion of ethylene and an internal acyclic mono- or polyene having four or more carbon atoms to produce other olefins having a lower number of carbon atoms than that of the acyclic mono- or polyene; for example, the conversion of ethylene and 4-methylpentene-2 yields 3-methylbutene-1 and propylene;
(4) The conversion of ethylene or an acyclic mono- or polyene having three or more carbon atoms and a cyclic polyene to produce an acyclic polyene having a higher number of carbon atoms than that of any of the starting materials; for example, the conversion of cyclohexene and 2-butene yields 2,8-decadiene; the conversion of 1,5-cyclooctadiene and ethylene yields 1,5,9-decatriene;
(5) The conversion of one or more cyclic mono- or cyclic polyenes to produce a cyclic polyene having a higher number of carbon atoms than any of the starting materials; for example, the conversion of cyclopentene yields 1,6-cyclodecadiene;
(6) The conversion of an acyclic polyene having at least seven carbon atoms and having at least five carbon atoms between any two double bonds to produce acyclic and cyclic mono- and polyenes having a lower number of carbon atoms than that of the feed; for example, the conversion of 1,7-octadiene yields cyclohexene and ethylene; or
(7) The conversion of one or more acyclic polyenes having at least three carbon atoms between any two double bonds to produce acyclic and cyclic mono- and polyenes generally having both a higher and lower number of carbon atoms than that of the feed material; for example, the conversion of 1,4-pentadiene yields 1,4-cyclohexadiene and ethylene.
In the prior art there are a number of catalysts for such disproportionation reactions. One type of catalyst comprises rhenium oxide and a support such as alumina, silica, silica-alumina, magnesia-titania, or thorium phosphate. Catalysts comprising rhenium oxide on thorium phosphate support while being interesting have generally been found to have lower activity than some of the other catalysts.
An object of the present invention is to provide a means for increasing the disproportionation activity of a rhenium oxide-thorium phosphate.